Check Out The Arduboy!

The Arduboy is a business card sized gameboy like device currently looking for backing on Kickstarter. Become one of the first 1000 people to back this project, and you’ll be able to get it for $29 (+5 shipping to US). The regular price is expected to be $39 after that. If it meets funding it should be released in Oct 2015.

I jumped on it, seems like a great size for for quick and easy gaming on the go. All games are going to be open source and free.